import java.util.*;

public class BinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    //建立二叉树
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        TreeNode root = A;
        return root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        System.out.print(root.val +" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    public void inOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    public void postOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    //非递归中序遍历二叉树
    public List<Character> inorderTraversal(TreeNode root) {
        List<Character> list = new LinkedList<>();
        Stack<TreeNode> stack = new Stack<>();
        TreeNode cur = root;
        while(cur != null || !stack.isEmpty()) {
            while(cur != null) {
                stack.push(cur);
                cur = cur.left;
            }
            TreeNode top = stack.pop();
            list.add(top.val);
            cur = top.right;
        }
        return list;
    }

    //获取节点的个数
    public int size(TreeNode root) {
        if(root == null) {
            return 0;
        }
        return size(root.left) + size(root.right) + 1;
    }

    //获取二叉树的高度
    public int getHeight(TreeNode root) {
        if(root == null) {
            return 0;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return Math.max(leftHeight, rightHeight) + 1;
    }

    //获取叶子节点的个数
    public int getLeafNodeCount2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }
}
